Blue blocking (400-500 nm radiation) and violet blocking (400-440 nm) chromophores have been incorporated into plastics used as ophthalmic lenses (e.g. spectacles, intraocular lenses and contact lenses). Blue blocking and violet blocking agents are reported to protect the retina against damaging higher energy visible light radiation. Ultraviolet blocking agents are also added to ophthalmic lenses to protect the retina against UV-A radiation. Together, blue blocker and UV absorber, absorb the damaging radiation spectrum that can potentially reach the retina.
U.S. Pat. No. 5,470,932, for example, teaches against the use of vinyl-functionalized dyes in acrylate-based polymer systems, recommending the use of acrylate polymerizable groups. The inventor argues that yellow dyes having acrylate or methacrylate functional groups are more efficiently bound by covalent bonds into acrylate polymers than a dye that has vinyl functionality. An example of a vinyl polymerizable dye cited in this patent, i.e., 4-phenylazophenol allyl ether, suggests that the formulation of such dyes is inefficient, in that a 44% absorption loss is reported after soxhlet extraction in acetone.
Accordingly, there is a need for an ophthalmic lens light blocking system which avoids the aforementioned problem in the prior art.